High sensitivity C-reactive protein (Hs-CRP) remains highly stable in long-term archived human serum.

BACKGROUND

The stability of biomarkers in stored biomedical samples is crucial, especially when storage is for extended periods of time. High-sensitivity CRP (Hs-CRP) is a biomarker of low grade inflammation that is extensively used to identify and study cardiovascular and/or inflammatory processes in clinical care and large epidemiologic studies. Therefore, assessing Hs-CRP stability in archived samples at a given temperature is important to ensure precision of measurements over time and the validity of studies using archived samples.

METHODS

We evaluated the stability of Hs-CRP in 30 randomly selected human serum samples by measuring Hs-CRP concentrations in freshly collected sample [Hs-CRP (0)] and in the same set of samples after 7-11years of storage at -80°C [Hs-CRP (LT)].

RESULTS

Hs-CRP did not significantly change up to 11years of storage at -80°C as shown by a negligible median difference between Hs-CRP (0) and Hs-CRP (LT), delta(Hs-CRP (0)-Hs-CRP (LT))=-0.01, p=0.45. There was a good concordance and agreement between Hs-CRP (0) and Hs-CRP (LT) as measured respectively by Lin's coefficient of correlation (ρC=0.98) and Bland-Altman analysis (mean difference=-0.02, 95% CI [-0.04-0.0045] p=0.107). In addition, the data also suggest that the time elapsed between collection and Hs-CRP measurement does not affect Hs-CRP stability over time when samples are kept under the appropriate conditions.

CONCLUSIONS

Long-term storage at -80°C for up to 11years did not significantly affect the stability of serum Hs-CRP. Given the cost and time for collecting fresh samples, this observation represents an important finding for biomedical research and clinical care.